The present invention is in the optoelectronics field. The invention specifically concerns devices relying on the elemental silicon for stimulated emissions. According to the invention, efficient optical emissions are obtained from elemental silicon in response to electrical or optical excitation. No such capability from elemental silicon has been previously demonstrated, and is produced in the invention through a new class of material, referred to herein as silicon nanoparticles.
A wide range of optoelectronic devices require stimulated emissions of light. Stimulated emissions are amplified and controlled light emissions. A trend is toward using optoelectronic signaling to replace signaling which relies upon conduction of electricity. Such optoelectronic signaling depends upon devices which produce stimulated emissions, such as lasers and optical amplifiers. In general, optoelectronic signaling is superior for its speed and immunity to many types of interference which affect electric signaling. It is expected that a significant leap will be realized, for example, with the perfection of computers that utilize optical signals instead of electric signals.
Many current communication systems already rely upon optical signals transmitted through optical fibers. Such systems require generation of stimulated emissions which can be modulated to transmit information. The systems may also rely upon amplification, also known as pumping, of optical signals to account for attenuation of signals over transmitted distances. Computers and communications systems are but two examples of devices which can benefit from use of optical signaling. Generally, any electronic device which uses electrical signaling may benefit from use of optical signaling instead.
There are also classes of devices which are unique to optical emissions. Laser light has many applications ranging from surgical devices, to manufacturing tools, to testing devices. Like the signaling devices, these varied devices require a source of stimulated emissions.
Group III-V semiconductors have been the primary source for obtaining stimulated emissions from a compact, semiconductor scaled devices. Group III-V materials are known as direct semi conductors. Direct semi conductors are devices in which the efficiency is as high as 30%. The Group III-V semiconductors can accordingly respond to electrical excitation with the production of significant stimulated emissions. A Group III-V layer typically forms the essential component of semiconductor devices which require stimulated emissions.
Manufacture of the Group III-V semiconductors is relatively difficult and expensive. The manufacture generally involves reactants and by-products which are hazardous. Often, separate steps and reaction chambers are required to produce the Group III-V materials thereby adding expense to the processes from which the materials are produced. Group III-V materials do not integrate well in silicon devices because of lattice mismatch. Hence integration of optics and silicon electronics is generally not considered possible with Group III-V semiconductors.
Elemental silicon, the widespread basis for electronic devices, is obviously suitable for integration into existing electronic structures. However, element silicon is an indirect semiconductor and therefore does not provide a basis for stimulated emissions. It has an extremely poor emission efficiency due to the fact that it is an indirect gap material. For indirect gap materials, emission of light requires the simultaneous release of a photon and participation of crystal vibrations in the form of phonon emission. This is the primary reason that artisans have looked to the Group III-V materials to provide stimulated emissions in electronic devices. Production of emissions from silicon would have advantages from the standpoint of its abundance as a source, and its relative benign nature compared to the components and by-products of processes used to form the Group III-V materials, and most importantly its potential of optoelectronic integration
Recently, some artisans have caused porous silicon to produce light. It was first discovered in 1990 by Canham. However, stimulated emissions have not been demonstrated from porous silicon despite an abundance of experimentation and papers that have been published on the subject. Moreover, porous silicon is usually only 1-5 percent efficient. This is due, in part, to the fact that elemental silicon sub structure is not small enough and it is typically plagued with impurities and electronic defects that compete very strongly with the radiative process.
Accordingly, it is an object of the present invention to provide a heretofore unknown source for stimulated emissions in electronic devices, elemental silicon nanoparticles.
An additional object of the present invention is to provide devices which produce stimulated emissions from elemental silicon nanoparticles.
The present invention relies upon a previously unknown material as an emission source or gain media, silicon nanoparticles. This new material and a method for making the same are described in copending application Ser. No. 09/426,389, to Nayfeh et al. entitled SILICON NANOPARTICLES AND METHOD OF MAKING THE SAME. These nanoparticles, having dimensions on the order of one nanometer and about having about 1 part per thousand or less larger than 1 nm exhibit qualities unlike bulk or atomic silicon. The silicon nanoparticles may be formed into random geometric structures. The silicon nanoparticles may also be suspended in fluids, incorporated into solids, formed into crystals, and formed into device quality thin films. The nanoparticles thus form the basis for a wide range of novel devices.
The present invention thus provides elemental silicon; in the form of silicon nanoparticles having about 1 part per thousand or less larger than 1 nm, capable of stimulated emissions as the basis for devices requiring production of stimulated emissions or a gain medium. Silicon particles of the invention produce stimulated emissions as the basis for stimulated emissions in electronic devices. Crystals formed of nanoparticles produce directed emissions, indicating the nanoparticles"" capability for lasing. Artisans will readily appreciate the broad ranging applicability of the invention as the basis for many devices which utilize stimulated emissions.